The instant application should be granted the priority dates of Oct. 18, 2005, the filing date of the corresponding German patent application 10 2004 030 063.1, as well as Mar. 8, 2005, the filing date of the International patent application PCT/EP2005/002441.
Rotating field machines of the type under consideration are also designated as bell-shaped rotors. They generally have a stationary inner and outer stator and a rotatably mounted rotor, whereby the latter is formed by a bell. Permanent magnet elements can be disposed in the bell for a magnetic bias.
The requirements regarding regulatability and the dynamics of electric motors constantly increase. A decisive criterion of the properties of electric motors is therefore the moment of inertia of the rotor or the quotient of generated torque and moment of inertia of the rotor. Particularly good characteristics in this regard are demonstrated by bell rotors, which, however, have a limited torque due to the unidirectional transfer of torque, since the rotor twists too greatly as the torque increases. In addition, bell-shaped rotors have problems with regard to heat dissipation, so that also for this reason the permissible power absorption is limited, which is particularly true if the bell is made of a polymeric material or a winding. In the article by W. R. Canders, H. Masebach, F. Laube “Technologies and Limits of High Torque Drives”, page 17ff, a bell-shaped rotor having a rotor provided of permanent magnets is described. The rotor is mounted on the end face bf the housing as well as on the shaft. The permanent magnets are disposed in the rotor between outer and inner stators, whereby not only the outer stator but also the inner stator each carry magnet or excitation coils. The described drives are slowly rotating drives having high torque, whereby the rotor for the most part is comprised of soft iron, resulting in a high moment of inertia. On page 19 of the article, a rotor having only one row of permanent magnets is illustrated, thus leaving to speculation how the permanent magnets are mounted in the rotor. With this embodiment, the outer and inner stators, together with the permanent magnets of the rotor, form a common magnet circuit.
No expedient nor reliable mounting of the permanent magnet elements is disclosed in the above mentioned article. In particular for rapidly rotating field machines, the mounting of the permanent magnet elements pursuant to the article by W. R. Canders is not suitable.
It is therefore an object of the present invention to provide a bell-shaped rotor drive for high speeds having great torque, according to which the permanent magnet elements are reliably mounted.